CHF3双频电容耦合放电等离子体特性研究

研究了用于SiCOH 低介电常数薄膜刻蚀的CHF₃气体在1356 MHz/2 MHz,2712 MHz/2 MHz和60 MHz/2 MHz双频电容耦合放电时的等离子体性质.发现2 MHz低频源功率的增大主要导致F基团密度的增大;而高频频率从1356,2712增大到60 MHz,导致CF₂基团的密度增大和电极之间F基团密度的轴向空间不均匀性增加.根据电子温度的分布规律及离子能量随高频源频率的变化关系,提出CF₂基团的产生主要通过电子-中性气体碰撞,而F基团的产生是离子-中性气体碰撞的结果.     

纤维状TiO2/Bi2O3光催化剂的制备及其光催化性能

以C₁₆H₃₆O₄Ti和Bi(NO₃)·5H₂O为原料,以棉花纤维为生物模板,合成了系列纤维状TiO₂/Bi₂O₃光催化剂．采用XRD、SEM、UV-Vis等测试技术对样品的相结构、形貌和吸光性能等进行了表征分析．结果表明,样品中的Bi₂O₃为单斜相和四方相共存的混晶,纤维长度达到毫米级,     

Al2O3Hx(x=1—3)分子团簇的结构与光谱研究

用密度泛函理论(DFT)的B3lyp方法在6-311++g(d,p)水平上对Al₂O₃H_x(x=1—3)分子的几何构型, 电子结构, 振动频率等性质进行了系统研究. 并给出了它们可能基态结构的总能量(E_T), 零点能(E_z), 摩尔热容(C_v), 标准熵(S), 原子化能(ΔE_m), 垂直电离能(IP)及垂直电子亲和能(E_A). Al₂O₃H和Al₂O₃H₂分子可能的基态的几何构型都为平面结构. Al₂O₃H₃的两个可能为基态的几何构型都是在立体Al₂O₃(D_3h)的几何结构基础上加三个氢原子构成. 这三个分子的能量最低结构为Al₂O₃H(²A′)C_s, Al₂O₃H₂(¹A′) C_s, Al₂O₃H₃ (²A) C₁.     

非线性光学晶体HgGa2S4 和 Hg0.5Cd0.5Ga2S4的能带结构、化学键及光学性质研究

用密度泛函理论和非谐振子模型计算了晶体HgGa₂S₄和Hg_0.5Cd_0.5Ga₂S₄的能带结构、态密度、化学成键及线性、非线性光学性质。结果表明：HgGa₂S₄的价带顶部主要是Ga-S成键态的贡献，导带底部主要是Ga-S反键态的贡献; Hg_0.5Cd_0.5Ga₂S₄的价带顶部主要由S-3p轨道组成，导带底部主要是Ga-S反键态的贡献。布居分析表明Ga-S键主要是共价成分，而Hg-S和Cd-S键主要是离子成分。HgGa₂S₄的折射率计算值与实验值在低能量区很好吻合。另外，HgGa₂S₄的能隙计算值比Hg_0.5Cd_0.5Ga₂S₄小，而二阶非线性极化率比Hg_0.5Cd_0.5Ga₂S₄大。     

不同初始温度下H2/O2混合物等离子体的演化

本文对不同初始温度下,H₂/O₂混合物等离子体中主要粒子随时间发展的演化规律进行了数值模拟,得到了放电后等离子体中主要带电粒子和中性粒子密度随时间的变化规律.计算结果表明,H₂/O₂混合物等离子体中主要活性粒子密度随时间的增加减小,化学反应达到平衡所需的时间随初始温度升高逐渐减少.     

锂离子正极材料正交相γ-LiV2O5的制备及性能

分别采用LiOH·H₂O, NH₄VO₃, HNO₃, C₂H₅OH作为原料在没有PVP和有PVP存在下合成了棒状和棒束状两种相貌的γ-LiV₂O₅. 棒状γ-LiV₂O₅材料中棒的直径为500～800 nm,而棒束状的γ-LiV₂O₅材料则是直径为100～600 nm的棒组成的,形貌比较均匀. 同时研究了此体系中γ-LiV₂O₅的合成机制. 将合成的材料进行电化学测试,棒束状的γ-LiV₂O₅ 的电化学性能更好,在电流密度为30 mA/g时的初始放电比容量为269.3 mAh/g,循环20次之后容量仍保持在228 mAh/g.     

H2O2水热合成双峰介孔硅MCM-48球

在温和的条件下,通过H₂O₂水热处理预合成的MCM-48,得到了有序的双峰介孔硅MCM-48球． 结果表明H₂O₂对于同时去除有机模板剂及形成双峰介孔硅MCM-48球具有重要的作用．采用XRD、TEM、FT-IR和N₂吸附-解吸等方法对双峰介孔MCM-48材料进行了表征,对双峰介孔MCM-48的形成机理也进行了探讨．     

三明治结构Tan(B3N3H6)n+1 团簇的磁性和量子输运性质

利用密度泛函理论和非平衡格林函数方法, 本文对小尺寸团簇Ta_n(B₃N₃H₆)_n+1 (n ≤ 4)的磁性和量子输运性质进行了系统的研究. 计算结果表明, 此类体系采用三明治结构作为其基态并且具有较高的稳定性. 体系的磁矩随团簇尺寸的增大而线性增大. 当把Ta_n(B₃N₃H₆)_n+1团簇耦合到Au电极上时, 形成的Au-Ta_n(B₃N₃H₆)_n+1-Au体系在有限偏压下展示出了较强的自旋过滤能力, 因而可以被看做是一类新型的低维自旋过滤器.     

CH4/H2和CH4/He体系等离子体发射光谱分析

 在CH₄/H₂和CH₄/He和CH₄/He两种系统中,利用光学发射谱技术对螺旋波放电产生低压甲烷等离子体内活性粒子的光学发射特征进行了原位诊断。在实验中,两种体系下同时都测得的主要荷电粒子为CH,Ha,Hb,Hg以及H2等。研究了各实验参数对这些活性粒子CH, Ha,Hb以及Hg的发射光谱强度的影响。结果表明：在CH₄/H₂体系下,随着射频功率的增大,Ha,Hb,Hg以及CH基团的相对强度都随着增加,而当放电气压变化时它们都呈现先增大而后减小的趋势。在CH₄/He体系下,随射频功率的增加,Ha,Hb,Hg以及CH相对强度变化的总体趋势也都是先增加而后减小,当工作气压增加时,Ha,Hb以及Hg的相对强度变化也是呈现先增大而后减小,但CH基团的相对强度却是逐渐减小的;这些结果为等离子体沉积各种薄膜过程的理解及制备工艺参数的调整提供了参考。     

羟基碳纳米管吸附SF6放电分解组分的DFT计算

本文根据密度泛函理论(density functional theory , DFT), 采用MS分子动力学仿真软件对羟基修饰的单壁碳纳米管(SWNT-OH) 吸附SF₆局部放电分解的四种主要组分SOF₂, SO₂F₂, SO₂和CF₄进行了详细的理论计算, 通过分析气体分子和SWNT-OH的前线轨道, 吸附过程中吸附能、电荷转移量和电子态密度的情况, 以及吸附前后SWNT-OH能隙的变化, 评判了SWNT-OH对气体分子的敏感性和选择性, 给出了SWNT-OH是否可以制备气体传感器检测SF₆局部放电分解组分的理论依据.     

使用发射光谱对感应耦合CF4/CH4等离子体中C2基团形成机理的研究

利用强度标定的发射光谱法，研究了感应耦合CF4₄/CH4₄等离 子体中空间基团的 相对密度随宏观条件（射频输入功率、气压和流量比）的变化情况. 研究表明：在所研究的 碳氟/碳氢混合气体放电等离子体中除了具有丰富的CF，CF2₂，CH，H和F等活 性基团外 ，还同时存在着C2₂基团，其相对密度随着放电功率的提高而增加；随着气压 的上升呈 现倒“U”型的变化. C2₂随流量比R（R=［CH4 _{关键词： 发射光谱 感应耦合等离子体 2}基团')" href="#">C2₂基团     

Flame structure studies of rich ethylene-oxygen-argon mixtures doped with CO2, or with NH3, or with H2O

Structures of several premixed ethylene-oxygen-argon rich flat flames burning at 50 mbar have been established by using molecular beam mass spectrometry in order to investigate the effect of CO₂, or NH₃, or H₂O addition on species concentration profiles. The aim of this study is to examine the eventual changes of profiles of detected hydrocarbon intermediates which could be considered as soot precursors (C₂H₂, C₄H₂, C₅H₄, C₅H₆, C₆H₂, C₆H₄, C₆H₆, C₇H₈, C₆H₆O, C₈H₆, C₈H₈, C₉H₈ and C₁₀H₈). The comparative study has been achieved on four flames with an equivalence ratio (f) of 2.50: one without any additive (F2.50), one with 15% of CO₂ replacing the same quantity of argon (F2.50C), one with 3.3% of NH₃ in partial replacement of argon (F2.50N) and one with 13% of H₂O in replacement of the same quantity of argon (F2.50H). The four flat flames have similar final flame temperatures (1800 K).CO₂, or NH₃, or H₂O addition to the fresh gas inlet causes a shift downstream of the flame front and thus flame inhibition. Endothermic processes CO₂ + H = CO + OH and H₂O + H = H₂ + OH are responsible of the reduction of the hydrocarbon intermediates in the CO₂ and H₂O added flames through the supplementary formation of hydroxyl radicals. It has been demonstrated that such processes begin to play at the end of the flame front and becomes more efficient in the burnt gases region.The replacement of some Ar by NH₃ is responsible only for a slight decrease of the maximum mole fraction of C₂H₂, but NH₃ becomes much more efficient for C₄H₂ and C₅ to C₁₀ species. Moreover, the efficiency of NH₃ as a reducing agent of C₅ to C₁₀ intermediates is larger than that of CO₂ and H₂O for equal quantities added.     

New FIR laser lines from optically pumped C2H3F, C2H3Cl, C2H3Br, C2H3CN, C2H5F, CH2CF2, HCOOH and CH3Br

Twenty-seven new cw far infrared laser lines with wavelengths between 137 and 988m have been observed from optically pumping C₂H₃F, C₂H₃Cl, C₂H₃Br, C₂H₅F, C₂H₃CN, CH₂CF₂, HCOOH and CH₃Br with a CO₂ laser. The wavelengths of these FIR laser lines were determined together with their optimum pressures and relative intensities.     

Collision-induced simultaneous transitions in H2+CF4 and H2+SF6 mixtures

The simultaneous transitions of the v₃ fundamental vibrations of CF₄ and SF₆ with the fundamental Q branch and S(1) line of H₂ have been studied for various H₂+CF₄ and H₂+SF₆ mixtures at total pressures up to 185 bars. The integrated intensities are found to be proportional to the partial densities of the gas mixture components. The agreement between experimental and calculated intensities is generally better for the Kihara potential than for the Lennard-Jones potential.     

The stability, frontier orbitals, bond character, and static linear polarizability of the fluorinated fullerene H20@C80F60

This paper uses the density functional theory under generalised gradient approximation to analyse the stability,frontier orbitals,bond character,and static linear polarizability of H20@C80F60,which has not been isolated,as well as those of the synthesised H 20 @C 80 H 60.The H20@C80F60 should be considerably stable by analysing its energy and aromaticity.The inside H and outside X will play different role in the chemical reaction involving H 20 @C 80 X 60(X=H and F).The covalence of C-H bond is in the order that the inside C-H bond of H20@C80F60 > the inside C-H bond of H 20 @C 80 H 60 > the outside C-H bond of H 20 @C 80 H 60,whereas the C-F bond of H20@C80F60 have both the covalent and ionic characters.The static linear polarizabilities of C 80 and H 20 @C 80 X 60(X=H and F) are all isotropic.     

Spatial distribution of SiCln （n=O-2） in SICl4 plasma measured by mass spectroscopy

For a better understanding of the deposition mechanism of thin films in SiCl4 source gas, we have measured the spatial distributions of SiCln （n=0-2） radicals in SICl4 radio frequency glow discharge plasma utilizing a mass spectrometer equipped with a movable gas sampling apparatus. The experimental results demonstrate that the relative densities of SiCln （n=0-2） radicals have peak values at the position of 10 mm above the powered electrode along the axial direction; the relative densities of the Si and SiCIn （n=1, 2） radicals have peak values at the positions of 27mm and 7 mm away from the axis along the radial direction, respectively. Generally speaking, in the whole SICl4 plasma bulk region, the relative density of Si is one order of magnitude higher than that of SICl, and the relative density of SiCl is several times higher than that of SICl2. This reveals that Si and SiCl may be the primary growth precursors in forming thin films.     

H2对Ar稀释SiH4等离子体CVD制备多晶硅薄膜的影响

以SiH₄，Ar和H₂为反应气体，采用射频等离子体化学气相沉积方法在300℃下制备了低温多晶Si薄膜.实验发现，反应气体中H₂的比例是影响薄膜结晶质量的重要因素，在适量的H₂比例下制备的多晶Si薄膜具有结晶相体积分数高，氢含量低，生长速率快、抗杂质污染等特性. 关键词： 低温多晶Si薄膜 等离子体CVD 4')" href="#">Ar稀释SiH₄ 2比例')" href="#">H₂比例     

工作压强对射频辉光放电H2/C4H8等离子状态的影响

利用辉光放电技术采用等离子体质谱诊断的方法研究了不同工作 压强下H₂/C₄H₈混合气体等离子体中 主要正离子成分及其能量的变化规律, 并分析了压强对H₂/C₄H₈混合气体的离解机理以及主要正离子形成过程的影响. 结果表明: 随着工作压强的增加, 碳氢碎片离子的浓度和能量均逐渐减小. 当工作压强为5 Pa时, H₂/C₄H₈混合气体等离子体中C₃H₅⁺相对浓度最大; 压强为10 Pa时, C₃H₃⁺相对浓度最大; 压强为15, 20 Pa时, C₂H₅⁺相对浓度最大; 压强为25 Pa时, C₄H₉⁺相对浓度最大. 对H₂/C₄H₈等离子体中的主要组分及其能量分布所进行的定性分析, 将为H₂/C₄H₈混合气体辉光放电聚合物涂层的工艺参数优化提供参考技术基础. 关键词： 辉光放电技术 等离子体质谱诊断 工作压强     

SnO2/TiO2 mixed oxide particles synthesized in doped premixed H2/O2/Ar flames

SnO₂/TiO₂ mixed oxides with primary particle size ranging between 5 nm d_p 12 nm were synthesized by doping a H₂/O₂/Ar flame with Sn(CH₃)₄ and Ti(OC₃H₇)₄ co-currently. The effects of “flow coordinate,” concentration and flame configurations were investigated with respect to particle size and morphology of the generated mixed oxides. In situ characterization of the mixed oxides was performed using the particle mass spectrometer (PMS), while XRD, TEM, BET and UV–Vis were performed ex situ. Results obtained showed that primary particle size of mixed oxides can be controlled by varying experimental parameters. The mixed oxides have interesting properties compared to those of the pure oxides of TiO₂ and SnO₂, which were also synthesized in flames earlier. Band gap tuning opportunities are possible using mixed oxides.     

Comparison of CH4/H2 and C2H6/H2 inductively coupled plasma etching of ZnO

CH₄/H₂-based discharges are attractive for dry etching of single crystal ZnO because of their non-corrosive nature. We show that substitution of C₂H₆ for CH₄ increases the ZnO etch rate by approximately a factor of 2 both with and without any inert gas additive. The C₂H₆/H₂/Ar mixture provides a strong enhancement over pure Ar sputtering, in sharp contrast to the case of CH₄/H₂/Ar. The threshold ion energy for initiating etching is 42.4 eV for C₂H₆/H₂/Ar and 59.8 eV for CH₄/H₂/Ar. The etched surface morphologies were smooth, independent of the chemistry and the Zn/O ratio in the near-surface region was unchanged within experimental error after etching with both chemistries. The plasma etching improved the band-edge photoluminescence intensity and suppressed the deep level emission from the bulk ZnO under our conditions, due possibly to removal of surface contamination layer.